Strengthening of cerebello-cortical connectivity to improve balance in older adults with mild balance problem: a brain stimulation study

Each year, one in three Australians aged over 65 falls. As the incidence of falls and fall-related injury increases, the likelihood of admission to hospital and residential aged-care increases [1]. The Australian fall-related healthcare burden is expected to be at least $1.4 billion per year unless effective prevention occurs [2, 3]. With 25% of the population predicted to be over the age of 65 by 2060 [4] and the high economic and personal burden associated with falls, we are set to face a health-funding crisis. Deficits in dynamic balance are a major cause of falls [5]. While some interventions can effectively reduce subsequent falls in ‘fallers’ [6], research targeting older adults with mild balance dysfunction—those who, without intervention, are very likely to progress to ‘faller’ status —is in its infancy [7]. Patients with mild balance dysfunction commonly experience near-falls that curtail activity and significantly increase the risk of an injurious fall [7]. Developing targeted, evidence-based interventions to improve dynamic balance in this patient group may reduce activity limitation, and improve confidence prior to a major fall. Aging is accompanied by decline in the quantity and quality of white matter, which results in anatomical disconnection of brain regions that usually function together; this results in impaired information transfer between brain regions, or ‘functional connectivity’. White matter integrity— indicative of effective functional connectivity—in the cortical motor network is associated with greater gait stability and reduced likelihood of falls [8]. White matter integrity is also positively associated with physical activity [9]. Recently, it has been shown that an exercise intervention can improve dynamic balance in people with mild balance dysfunction [7]. Neuroimaging studies show age-related decline in functional connectivity between the cerebellum and M1, which plays an important role in planning, timing, sequencing and execution of voluntary movement [10]. Therefore, characterising the role of altered functional connectivity in age-related movement deficits, and developing a targeted protocol to strengthen functional connectivity, is very likely to lead to substantial improvements in dynamic balance. Advanced high definition, transcranial direct current stimulation (tDCS) protocols developed during the last few years can be used to strengthen functionally relevant connections [12, 14]. The ability to strengthen functional connectivity is important: functional connectivity is shaped by both structural connections and short-term plastic changes [15]. Therefore, this project will characterize the relationship between age-related changes in the cerebello-primary motor cortex (M1) functional connectivity and dynamic balance in older adults with mild balance dysfunction and allows us to identify if we can use novel interventions to return these disturbed functional connectivity’s to a normal level in the future.